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United States Patent | 5,115,128 |
Cook | May 19, 1992 |
A resonant beam sensor is excited into resonance by directing onto it a drive signal comprising light which has been amplitude modulated at the resonant frequency. A portion of the drive signal reflected by the sensor is demodulated by a photodetector to provide a measurement signal.
Inventors: | Cook; Alan J. (Birmingham, GB2) |
Assignee: | Lucas Industries Public Limited Companies (Birmingham, GB2) |
Appl. No.: | 456787 |
Filed: | December 29, 1989 |
Jan 06, 1989[GB] | 8900304 |
Current U.S. Class: | 250/227.21; 250/227.27 |
Intern'l Class: | H01J 005/16 |
Field of Search: | 250/231.1,231.19,227.23,225,227.12,227.27,227.21 |
4451730 | May., 1984 | Brogardh et al. | 250/227. |
4562348 | Dec., 1985 | Brogardh et al. | 250/231. |
4772786 | Sep., 1988 | Langdon | 250/231. |
4933545 | Jun., 1990 | Saaski et al. | 250/227. |
Foreign Patent Documents | |||
0266974A2 | May., 1988 | EP. | |
3203347A | Aug., 1982 | DE. | |
2121953A | Jan., 1984 | GB. |